Former Florida Governor Jeb Bush is firing back at Donald Trump after the billionaire presidential candidate pointed out that 9/11 happened under his brother George W. Bush’s watch.

It’s not the first time that Bush has tangled with Trump over his brother’s record.

During the CNN Republican Presidential debate in California, Trump accused George W. Bush for being a disastrous president.

“Your brother – and your brother’s administration gave us Barack Obama, because it was such a disaster, those last three months, that Abraham Lincoln couldn’t have been elected,” Trump told Jeb Bush.

The crowd was mostly silent while Jeb Bush defended his brother.

“You know what. As it relates to my brother, there’s one thing I know for sure. He kept us safe,” Jeb Bush shot back, as the audience burst into applause.

“You remember the rubble?” he continued. “You remember the fire fighter with his arms around it? He sent a clear signal that the United States would be strong and fight Islamic terrorism, and he did keep us safe.”

The audience loved Bush’s defense of his brother, suggesting that they weren’t ready to condemn the former president.

But Donald Trump didn’t back down.

“I don’t know. You feel safe right now? I don’t feel so safe,” he responded.